Issue started one day when my PC booted to a black screen. Went into safe mode > Device Manager > Display adapters and disabled my GPU. This allowed it to boot normally so I uninstalled/reinstalled GPU drivers to no avail. I can't remember the exact order I did things in, but at some point I:

I have gotten Error 99, Error 173, and Error 175 while attempting to install drivers. My GPU is firmly connected to my motherboard including both power cables, and the fans are spinning. I'm now at a loss. Any help is hugely appreciated as I very much hope to avoid needing to buy a new GPU. Thank you. DxDiag Report attached.

I actually have an update since posting this thread. I realized that my motherboard has two PCIe ports, so I switched my card to the other one and this fixed the issue briefly. My monitor recognized my GPU and I was able to install the drivers without any errors. It rebooted normally but after a few minutes the screen went black, and now neither port will recognize the GPU. Also, sometimes the fans will not spin when plugging it in, and sometimes they spin too fast as if I'm running a game. It appears my last step might be to try the card in a different system, though the only other desktop in the house is a prebuilt Gateway.